An interesting yet brief discussion arose in the comments of my post yesterday on the Phillies’ lineup construction. Nik rightfully asked why I didn’t include Ruiz’s numbers after his 25-game suspension in my analysis. After making the adjustment, we discussed the merits of the surprisingly small three-run difference between a full season of Erik Kratz (projected .312 wOBA) and 120 games from Chooch (projected .340). I wrote:

[…] the general perception of Ruiz is probably a bit biased by his ridiculously good 2012 (.398 wOBA). His career average is .340.

Ruiz is now 34 years old, and 34-year-old catchers are rarely as productive as Ruiz was last season. He had a 149 adjusted OPS according to Baseball Reference, making him one of only four catchers all-time — and one of two since 1956 — to post an adjusted OPS of 145 or better at the age of 33 or older (min. 400 PA, 75% of games at catcher).

To say that 2012 was a career year for Ruiz, whose previous career-high wOBA was .368 and whose career average is .340, is an understatement. His batted ball rates went in all the right directions (though likely unsustainable):

Set a career-high with a .339 BABIP, one of only two seasons in which his BABIP exceeded .310

Set a career-low with an infield pop-up rate below six percent, well below 2011’s 13 percent and his career average nine percent

Set a career-high as 15 percent of his fly balls were home runs, ahead of 2011’s four percent and his sub-eight percent career average

In looking at his plate discipline and ground ball/fly ball ratios, not much changed from 2011 to 2012. He hit slightly fewer fly balls and slightly more line drives, but not enough to be statistically significant, and line drive rate isn’t very reliable in the first place. He saw similar amounts of pitches in the strike zone and swung at them at roughly the same rate. He saw similar amounts of fastballs and similar amounts of off-speed pitches as in 2011. Yet his isolated power jumped from .100 in 2011 (and .143 career) to .215.

There are very few catchers who have experienced such a power surge in recent times. Since 1990, there have been only 20 catchers that have posted a .200 or higher isolated power at the age of 30 or older. Two of them you’d expect: Mike Piazza and Jorge Posada, who had a handful of qualifying seasons. Two of them occurred last season: Ruiz and A.J. Pierzynski. Others to have multiple seasons include Chris Hoiles, Darren Daulton, Jason Varitek, and Mike Stanley. I took out all the repeat offenders and looked at players who had one year with a very high ISO. Here are the results, and a look at their ISO the following season:

Only two of the 12 listed catchers posted a better ISO the following season, while the other ten declined by no fewer than 32 points. Seven of the 12 never posted a better ISO than they did the year after, as they continued to decline and eventually retire.

Is there a reason to believe Ruiz is an outlier like Tettleton and Hundley? Ruiz has only displayed such power once (previous career-high ISO was .171 in 2009), while Tettleton had already posted a .251 ISO in 1989 and .185 in ’86. Hundley had four consecutive seasons with a .200 or better ISO from 1994-97.

Tettleton and Hundley also struck out a lot, each with a 23 percent career average strikeout rate compared to Ruiz’s 11 percent. Avoiding strikeouts is great, but taking big cuts is a big part of consistently hitting for power. Using data from 2010-12 with a sample size of 230 players, I found roughly a .2 r-square between strikeout rate and isolated power. Among those hitters, Ruiz had the 29th-lowest strikeout rate, and among those 29 hitters, he had the seventh-highest ISO. Among the 30 hitters with the highest strikeout rate, nearly half (14) had an ISO above .200.

ZiPS sees Ruiz’s ISO dropping down to .149, and as such there is a projected wOBA decline as well, from .398 to .340. His 2012 was certainly fun to watch, but there aren’t any reasons to expect him to continue it going forward, particularly given his age and his plantar fasciitis injury.